Easily loaded and unloaded getter device for reducing evacuation time and contamination in a vacuum chamber and method for use of same

ABSTRACT

A getter device is shaped like a substrate used in a deposition process. Embodiments of the device include a powdered getter material coated onto one or both sides of a support with a narrow rim portion left uncoated so that the device can be manipulated by automatic handling equipment. A method for using the getter device includes providing a vacuum chamber and automatic handling equipment, loading the device into the chamber, reducing the chamber pressure to a desired value by using the getter device in conjunction with an external pump, removing the getter device and replacing it with a substrate, and depositing a thin film on the substrate. The getter device can be in an activated state when loaded into the chamber, or it can be activated after being loaded by employing heating equipment ordinarily used to heat substrates placed in the chamber. The getter material of the device may also be activated in a separate activation chamber before the getter device is loaded into the vacuum chamber.

CLAIM OF FOREIGN PRIORITY PURSUANT TO 35 U.S.C. § 119

This application claims foreign priority under 35 U.S.C. §119 fromItalian Patent Application Serial Number MI99 A 000744 filed Apr. 12,1999, which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention provides a getter device advantageously shapedlike a substrate for use in a thin film deposition system and a methodfor its use.

2. Background

Processes for depositing thin films onto substrates are widely used inthe manufacture of a wide array of commercial products. Examples ofthese processes include the fabrication of integrated electroniccircuits (ICs) in which circuits are formed on a semiconductorsubstrate; the manufacture of data storage media, such as compact disks(CDs), where a thin layer of aluminum is deposited onto a substrate of atransparent plastic; the production of computer hard disks where amagnetic material is deposited onto a substrate such as aluminum; andthe production of flat panel displays in which active elements arecommonly created on glass substrates. Processes for depositing thinlayers are also being adapted to the developing field of micromechanicaldevices, where micron-scale mechanical structures are fabricated withsimilar techniques to those utilized in the production of ICs. The mainindustrial techniques for the deposition of thin layers include chemicaldeposition from the vapor phase and physical deposition from the vaporphase, widely known in the art as “chemical vapor deposition” and“physical vapor deposition” respectively or by their acronyms “CVD” and“PVD”.

In CVD processing, two or more gaseous species are caused to react in anevacuated chamber containing a substrate. The reaction product forms asolid deposit on the substrate in the form of a thin film or layer. Thedegree to which the chamber must be evacuated will vary according to theparticular CVD process employed. Some systems, those known aslow-pressure or alternately ultra-high vacuum, can require initialevacuations of the deposition chamber to a pressure value in the rangeof 10⁻⁸-10⁻⁹ mbar. Hereinafter, reference to CVD processing will referto the low-pressure variants unless stated otherwise.

Physical vapor deposition (PVD) actually encompasses a number ofdifferent techniques that all share the following common features:

-   -   a target formed of a material to be deposited, generally having        the shape of a squat cylinder or a disk, is positioned in a        deposition chamber in front of a substrate and parallel thereto;        and    -   the chamber is initially evacuated to a base pressure and        thereafter back-filled with an inert gas, generally argon or        another noble gas, to a pressure of about 10⁻²-10⁻⁵ mbar; a        potential difference of some thousands volts applied between the        supports of the substrate and the target (providing the latter        with a cathodic potential) generates a plasma of electrons and        positive ions in the space between the substrate and the target;        the positive ions are accelerated by the electric field into the        target causing atoms or “clusters” of atoms to erode or        “sputter” off of the surface of the target and into the        atmosphere of the chamber; material thus eroded condenses onto        the substrate to form a thin film or layer.        As is well known in the art, commercially useful processes        frequently include the deposition of a plurality of successive        thin layers which may be performed in a succession of deposition        chambers or in a single chamber configured to perform multiple        depositions. Hybrid processes, comprising aspects of both CVD        and PVD processes are also well known in the art.

It is further understood in the art that the properties of thin layerdevices, particularly ICs, are strongly dependent on the presence ofdefects within the deposited layers. These defects are most commonly dueto the inclusion of impurity atoms or molecules within the depositedlayers. Consequently, it is important to minimize the possible sourcesof contamination in all processing steps. For example, contamination canbe reduced by using components of the highest possible purity (reactivegases in the case of CVD, targets in case of PVD, and inert gasesgenerally) and ensuring the highest cleanliness of all surfaces withinthe production system and especially within the gas distribution systemand each deposition chamber.

Presently, to create high quality films and to do so with the greatestefficiency, thin film deposition processes are commonly performed insystems comprising a plurality of chambers, each configured for aspecific operation. For example, deposition steps are performed indeposition chambers, while conditioning chambers can be configured forcleaning or thermal processing steps like pre-heating substrates.Systems comprising multiple chambers can be arranged linearly such thatone is directly connected to the next. Alternatively, multiple chamberscan be disposed around a central transfer chamber.

Chambers are connected to one another by means of valves that arenormally opened only to allow the transfer of substrates from onechamber to another. Substrates are passed between chambers by automatedsubstrate handling equipment, in general mechanical arms that areconfigured to grasp or support a substrate typically along an edge bythe use of tangs, clamps, and guides. The valves and the automatedhandling equipment are typically configured to the dimensions of thesubstrates, and are thus designed to accommodate objects that are boththin and broad. Semiconductor substrates, for example, are generallycircular, often with a machined flat segment or notch to indicatecrystallographic orientation, with thicknesses between about 0.5 mm andabout 1 mm and lateral dimensions between about 150 mm to about 300 mm.Substrates used in the production of flat panel displays, on the otherhand, are commonly rectangular with thicknesses between about 1 mm and 5mm and lateral dimensions between about 10 cm and 1 meter.

In order to guarantee the highest cleanliness possible, all chambers aregenerally kept under vacuum with the highest vacuum levels beingmaintained in the deposition chambers. As is well known in the art,higher vacuum levels are typically achieved through the use of a seriesof pumps, each intended to operate in a different pressure range.Evacuation is typically initiated with a low-vacuum mechanical pump(e.g. a rotary pump) that is effective down to a pressure range of about10⁻² mbar. Lower pressures can be achieved with medium and high-vacuumpumps such as turbomolecular or cryogenic pumps.

A simple example of a process system comprising multiple chambersarranged around a transfer chamber will serve to illustrate the pathwaytraveled by a substrate. Substrates are initially arranged in a suitablyshaped carrier (e.g. a cassette or a pod) that is loaded into a firstchamber. The inner walls of the carrier are provided with tangs orguides for the purpose of keeping the substrates separate from eachother, and to simplify automated handling operations. A vacuum of about10⁻⁵-10⁻⁶ mbar is achieved in the first chamber after the substrates arefirst introduced, and then a valve is opened between the first chamberand the transfer chamber. A mechanical arm removes a substrate from thecarrier and transfers it to the transfer chamber where the pressure ismaintained at a level lower than those in the first chamber, generallyabout 10⁻⁷ mbar.

Next, a mechanical arm is employed, for example, to transfer thesubstrate from the transfer chamber to a deposition chamber through asecond valve. The mechanical arm places the substrate on a sample holdernear the center of the chamber. Typically, the sample-holder issupported on a pedestal that is moveable in some systems. The ability toheat the deposition zone, the region within the chamber surrounding thesample holder, is generally provided in deposition chambers both to helpdegas the pedestal during the initial stages of evacuation and topromote more homogeneous depositions. Deposition chambers are frequentlyprovided for this purpose with heating equipment, such as electricalresistors or infra-red lamps, to heat the deposition zone either fromthe inside or from the outside of the chamber through one or more quartzwindows.

The vacuum level required for thin film depositions in mostmanufacturing processes is generally about 10⁻⁸ mbar, which requiresbetween about 4 to about 12 hours to achieve. After a sufficient vacuumis obtained in a deposition chamber a thin layer can be depositedaccording to the technique for which the chamber is configured, forexample CVD or PVD. The technique may also include one or morepreliminary operations that need to be performed at the depositionvacuum level but before the actual deposition. After the deposition hasbeen completed the substrate can then be transferred, again by means ofautomated handling equipment and transfer chambers, either to anotherchamber or back to a carrier to be removed from the system.

Ideally, systems for depositing thin films should always be keptisolated from the atmosphere. However, vacuum chambers must be openedperiodically, for example, to perform maintenance on automatedcomponents, to clean interior surfaces, and in the case of PVD, toreplace exhausted targets or to switch to a different target in order touse the chamber to deposit a different material. Each time a chamber isbrought to ambient pressure its interior surfaces, the surfaces ofequipment disposed within the chamber, and the surfaces of any targetswill tend to adsorb atmospheric gases, in particular water vapor. Theseadsorbed gases are then continuously released into the chamber when thechamber is next evacuated. The balance between the release of adsorbedgases from interior surfaces, commonly known as degassing, and the gasremoval (“pumping”) speed of associated vacuum pumps substantiallydetermines the base pressure of the system, where the base pressure isthe lowest pressure attainable in a commercially reasonable length oftime.

Lowering the base pressure necessarily results in fewer impurities inthe process atmosphere and is therefore desirable. Base pressures aretypically between about 10⁻⁷ and about 10⁻⁹ mbar. At these vacuum levelsthe chamber cleanliness is generally considered acceptable for startinga new cycle of depositions. It will be appreciated, however, that insome instances it is desirable to perform depositions and otheroperations at a preset pressure above the level of the base pressure. Apreset value above the base pressure may be used, for instance, duringthe cleaning of a target and in other preliminary operations.Additionally, it may be desirable to use a preset value above the basepressure for depositions where film quality is acceptable at suchpressures. The further value inherent any time a preset value above thebase pressure is used is that it can be achieved more quickly than thebase pressure. Faster pump-down cycles lead to greater throughput andtherefore to greater yields per unit time.

Typically, in order to improve a base pressure, each time a chamber isevacuated after being opened to the atmosphere it is simultaneouslyheated to a temperature in the range of about 100° C.-300° C. Thistreatment is commonly known as “baking.” During a bake the rate ofdegassing from the surfaces within a chamber is increased, thus removingmuch of the gas initially adsorbed from the atmosphere. It is well knownthat degassing can be further increased by increasing the pumping speed.Thus, increasing the pumping speed during baking further reduces thequantity of residual adsorbed gases on surfaces within the chamber. Putanother way, more aggressive pumping during a baking operation resultsin a cleaner vacuum chamber.

All else being equal, providing a cleaner vacuum chamber whilemaintaining an equivalent pumping speed after baking will result in alower base pressure in the chamber. This is so because lowering theamount of residual adsorbed gas on interior surfaces reduces subsequentdegassing, and base pressure is a balance between degassing and pumpingspeed. It should also be noted that by providing a cleaner vacuumchamber while maintaining an equivalent pumping speed after baking onecan more quickly achieve a specific pressure value above the basepressure. Therefore, in situations where further reducing the basepressure is not considered important, one can bring a vacuum chamberdown to an operational pressure above the base pressure more quickly byimproving the pumping during baking.

In the case of PVD, targets are subjected to an additional cleaningtreatment after being exposed to the ambient atmosphere. This treatment,commonly known as “burn-in,” comprises performing a deposition on asacrificial substrate and requires between about half an hour and about4 hours. The deposition thus performed erodes away the contaminatedsurface of the target to expose a fresh clean surface. The contaminatedsurface material is deposited on the sacrificial, or “dummy,” substratewhich then may be discarded.

The use of getter materials and devices inside thin film depositionchambers has already been disclosed in patent application EP-A-693626,the publications of international patent application WO 96/13620 and WO97/17542, and in U.S. Pat. No. 5,778,682. The European patentapplication EP-A-926258, in the name of the assignee of the presentapplication, also discloses the use of getter systems in PVD processes.

Getter materials that have been used for the production of prior artgetter devices include metals such as zirconium (Zr), titanium (Ti),niobium (Nb), tantalum (Ta), and vanadium (V), and the alloys of thesemetals. Additionally, these metals, alone or in combination, have beenfurther combined with one or more other elements chosen from amongchromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni),aluminum (Al), yttrium (Y), lanthanum (La), and the rare-earth elements.Commercially popular getter materials include the binary alloys Ti—V,Zr—V, Zr—Fe and Zr—Ni and ternary alloys Zr—Mn—Fe and Zr—V—Fe.

Getter materials have been formed into getter devices by variousdifferent methods according to the prior art. Getter materials may beformed through traditional metallurgical processes such as casting andworking, but more commonly they are formed through powder metallurgy.Powder metallurgy allows the getter material to be prepared with atailored particle size distribution and to be sintered into a body withgood mechanical strength and a desired degree of porosity. For getteringpurposes, porosity is advantageous to increase the specific surface area(surface area/gram of material) of the getter material in contact withthe atmosphere to be pumped.

Where getter materials need to be applied in very thin layers othertechniques are often employed. A getter material deposited on a supportcan be obtained, for example, by PVD. The preparation of getter devicesby PVD is described in the publication of international patentapplication WO 97/49109. This technique provides the advantage ofallowing the deposition of a getter material onto many kinds ofsupports, including glasses and ceramics. Advantageously, depositsobtained by PVD techniques tend not to be sources of particlecontamination.

Additionally, getter materials can be deposited onto a support in theform of a powder. The deposition of powders can be carried out by coldrolling, as is well known in the field of powder metallurgy, howeverpowders can only be applied to metallic supports. Another technique isto spray a suspension of getter particles in a suitable solvent onto aheated support, as described in patent application WO 95/23425incorporated herein by reference. Furthermore the support may be coatedwith particles of a getter material according to an electrophoretictechnique. In this technique, however, the support must be electricallyconductive. Electrophoretic deposition techniques are described in U.S.Pat. No. 5,242,559 which is incorporated herein by reference. Finally,depositions of getter material powders onto supports can be carried outby a serygraphic technique, as described in the publication ofinternational patent application WO 98/03987, also incorporated hereinby reference. The serygraphic technique is particularly advantageousbecause it provides for depositing powdered getter materials onto widelydifferent types of supports including metals and insulators. Further,the serygraphic technique allows for the formation of patterned depositswhere a portion of a coated support surface, for example, remainsuncoated.

The references described above that teach getter devices, however,disclose only systems that are fixed within a vacuum chamber andcontinue to remain in the chamber while depositions or other processesare performed. A significant disadvantage of the foregoing prior art isthat substantial modifications are often required in order to configurea processing chamber to accommodate such getter devices and associatedhardware such as heaters and shields. These modifications increase thesize, the complexity, and the cost of a vacuum chamber, and increasedsize generally implies an increased internal volume and a longerevacuation time. Further, getter devices of the prior art are not easilyremoved from a chamber without opening it to the ambient atmosphere.

As is well known in the art, getter materials require for theiroperation an initial activation treatment at temperatures between about250° C. and about 900° C. for times ranging between about a few minutesand about an hour. The specific time and temperature necessary toactivate a getter will vary according to the particular composition ofthe getter material as well as other factors. It is further well knownthat activated getter materials cannot be exposed to partial pressuresof reactive gases higher than about 10⁻³ mbar, and that unactivatedgetter materials cannot be activated at such pressures, because eitheract can result in the combustion of the getter material.

It will be appreciated that not all gases are reactive with respect to agetter material, and therefore total pressures above about 10⁻³ mbar canstill be safe so long as the partial pressures of the reactive gasesremains below about 10⁻³ mbar. Reactive gases typically include speciessuch as oxygen, water, carbon dioxide, carbon monoxide, hydrogen, and insome instances nitrogen. Examples of gases that are non-reactive includethe noble gases such as helium and argon. Therefore, it would still besafe to introduce a getter material into a vacuum chamber containingargon at a pressure of about 10⁻² mbar so long as the sum of the partialpressures of any reactive gases remains below about 10⁻³ mbar. It wouldalso be safe, under such conditions, to activate a getter material.

It is an object of the present invention, therefore, to provide a getterdevice that can be easily transported into and out of an evacuatedchamber instead of being permanently installed. It is another object ofthe present invention to provide a method for the use of such a getterdevice for increasing the pumping of a vacuum chamber to achieve eithera lower base pressure or to reach a set operating pressure more quickly.

SUMMARY OF THE INVENTION

The present invention provides an easily loaded and unloaded getterdevice for reducing evacuation time and contamination in a vacuumchamber. The getter device comprises a getter body having essentiallythe shape of a substrate used in a deposition process. Forming thegetter body to have the same shape as a substrate allows the getterdevice to be loaded and unloaded with respect to a chamber by existingautomatic handling equipment already configured to load and unloadsubstrates. Further, the shape allows the getter device to be placedinto a substrate carrier for introduction into a processing system.Further still, most substrates are broad and thin, and a getter devicehaving such a shape will advantageously have a high surface area perunit weight of getter material. Some embodiments of the presentinvention are shaped. like semiconductor wafers use in semiconductorfabrication, while others are shaped like the rectangular substratesused in the production of flat panel displays.

A getter device of the present invention is preferably formed of apowder of at least one getter material. Fabrication from a powderprovides a high specific surface area for improved gettering capacity.Additional embodiments of the present invention are directed to a getterbody comprising a support and a first getter layer formed of at leastone deposit of a getter material on a first face of the support. Infurther embodiments the getter body further comprises a second getterlayer formed of at least one deposit of a getter material on a secondface of the support. Still other embodiments further include a firstuncoated rim portion on the first face of the support and a seconduncoated rim portion on the second face of the support. The support isadvantageous because it provides mechanical strength to the getter body.Uncoated rim portions allow getter devices of the present invention tobe manipulated by automated handling equipment typically configured tohandle substrates by their edges. Therefore, by leaving rim portionsuncoated, the clamps, tangs, and guides used by automated handlingequipment to transfer substrates will not come into contact with thegetter layers and create particulate contamination.

Providing a first getter layer on only a first face of the supportcreates a getter device suitable for use in deposition systems that areconfigured to deposit materials on only one side of a substrate, such asin semiconductor processing and in the manufacture of compact disks(CDs). In these systems a substrate is commonly supported on a sampleholder such that one face of the substrate rests in contact with theholder. Therefore, to avoid creating particulate contamination, it isdesirable to leave uncoated the face of the support that would contactthe holder. Similarly, some deposition systems are configured to depositonto both sides of a substrate, such as in the manufacture of hard disksfor computers. For these systems a getter device would be desirablewhere both sides of the support are coated with getter material tofurther increase its gettering capacity.

Getter devices of the present invention provide several advantages overthe prior art. Getter devices of the present invention do not need to bepermanently mounted within a process chamber. Consequently, getterdevices of the present invention may be readily used in conjunction withany vacuum chamber configured to accept a substrate, regardless ofwhether the chamber already includes a getter pump. An easilytransportable getter device also removes the need for mounting brackets,complex shielding to protect the getter material of the device, andadditional heaters to periodically activate the getter material.Eliminating brackets, shields, and heaters allows the chamber to have asmaller internal volume so it can be more rapidly evacuated to a desiredvacuum level. Removing these components can simplify the design andmanufacture of vacuum chambers and therefore help reduce their cost.Further, an easily transportable getter device can be removed from achamber without having to resort to a time consuming tear-down procedurethat exposes the chamber to the ambient atmosphere and thereafterrequires a lengthy re-assembly, bake-out, and pump-down.

The present invention also provides a method for increasing the yield ofa manufacturing process that includes the deposition of a thin layer ina vacuum chamber. The method comprises introducing a getter device intothe vacuum chamber before or during evacuation with the same automatedsubstrate handling equipment used for transferring substrates. Anunactivated getter device can be loaded before evacuation begins, andthen after a pressure of about 10⁻³ mbar or less has been achieved thegetter material can be activated with heaters configured to heat asubstrate. An activated getter device can be loaded after a pressure ofabout 10⁻³ mbar or less has been achieved in the chamber. Someembodiments of the method include activating the getter material in aseparate activation chamber before the getter device is loaded into thevacuum chamber. Further embodiments of the method provide for the use ofa getter device in a vacuum chamber where the total pressure is aboveabout 10⁻³ mbar, provided that the sum of the partial pressures of allreactive gases remains below about 10⁻³ mbar and the balance of theatmosphere within the chamber comprises non-reactive gases such as noblegases.

The method of the invention further includes continuing the chamberevacuation while maintaining therein the activated getter device until adesired pressure is achieved, and then removing the getter device fromthe chamber. Thereafter, a substrate can be loaded into the vacuumchamber and a deposition of a thin film performed. In some embodimentson the method of the present invention a preliminary operation, such asthe burn-in of a PVD target, is performed in place of a deposition.

The method of the invention is advantageous because it allows thepressure within a vacuum chamber both to be reduced to a preset valuemore quickly and to be reduced to a lower base pressure. A lower basepressure results in lower impurity levels within the vacuum chamberleading to higher quality films and higher production yields. The methodis also advantageous because it may be used with equipment that isn'tpresently configured to include a getter pump.

These and other aspects and advantages of the present invention willbecome more apparent when the detailed description below is read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, withlike reference numerals designating like elements.

FIG. 1 shows a getter device of the present invention comprising agetter body;

FIG. 2 shows another embodiment in which the getter body includes asupport with a getter material layer;

FIG. 3 shows another embodiment in which the getter body includes asupport with two getter material layers;

FIG. 4 shows a flow chart that illustrates a method of the presentinvention;

FIG. 5 shows a flow chart that illustrates an alternative embodimentthereof;

FIG. 6 shows a flow chart that illustrates another alternativeembodiment thereof;

FIG. 7 shows a flow chart that illustrates a further alternativeembodiment thereof;

FIG. 8 shows a flow chart that illustrates still another alternativeembodiment thereof; and

FIG. 9 shows a comparison of the pressure in a PVD chamber duringpump-down cycles performed according to the prior art and according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a getter device 10 according to one embodiment of the presentinvention. The getter device 10 comprises a getter body 12 havingessentially the shape of a substrate used in a deposition process. Thoseskilled in the art will appreciate that because the getter body 12 hasessentially the same shape as a substrate it may therefore bemanipulated by automatic handling equipment configured to transportsubstrates. Consequently, the getter device 10 of the present inventionmay be easily loaded and unloaded by automatic handling equipment intoand out of any chamber that is configured to accept a substrate.

Getter body 12 has essentially the same shape as a substrate used in adeposition process. Therefore, a getter body 12 to be used in asemiconductor fabrication system should be essentially circular with athickness between about 0.5 mm and about 1 mm and a lateral dimensionbetween about 150 mm to about 300 mm. A getter body 12 for use insemiconductor fabrication can also include a flat segment as would asemiconductor substrate. Likewise, a getter body 12 to be used in theproduction of flat panel displays should be essentially rectangular witha thickness between about 1 mm and 5 mm and a lateral dimension betweenabout 10 cm and 1 meter.

Getter body 12 can be formed of any getter material known in the art,however, some compositions will be preferable for a particularapplication due to various considerations. For example, certain speciesof contaminants like water vapor may be especially problematic in aparticular process and a getter with a composition more favorable togettering water vapor would therefore be desirable. A getter materialgenerally suited to the purposes of the present invention is an alloymanufactured and sold by the assignee of this application under the nameSt 787. St 787 has a composition of 80.8 weight percent Zr 14.2 weightpercent Co and 5 weight percent A, where A may be any element chosenfrom the group including yttrium, lanthanum, and the rare earth elementsor any mixture thereof. Other alloys manufactured and sold by theassignee that are generally suited to the present invention include analloy with a composition of 84 weight percent Zr and 16 weight percentAl distributed under the name St 101®, and an alloy with a compositionof 70 weight percent Zr 24.6 weight percent V and 5.4 weight percent Fedistributed under the name St 707. Mechanical mixtures of the two lastcited alloys with either zirconium metal or titanium metal can beadvantageous due to their good mechanical characteristics and resistanceto particle shedding. An example of such a mixture is manufactured andsold by the assignee under the name St 121. This mixture comprises 70weight percent titanium powder and 30 weight percent of a powder of St101®.

The getter body 12 may be formed from sheet, cast as an ingot andsliced, or made from powder compacted under high pressure, however, itis preferably made by sintering a powder of at least one gettermaterial. Sintering provides for good mechanical strength as well as theability to control the porosity of the getter body 12. However,substrates used in deposition processes are commonly both broad andthin, and a sintered getter body 12 having such a shape and a desirablyhigh porosity may not have sufficient mechanical strength. Were a getterbody 12 to fail for insufficient mechanical strength it could easilydamage automated handling equipment and contaminate vacuum chambers andsystems with particulates.

Consequently, it is preferable to form a getter layer 22 of a gettermaterial onto a support 24 provided to impart additional mechanicalstrength. FIG. 2 illustrates a getter device 20 formed of a getter layer22 on a substrate 24 and that can be used in a system for manufacturingflat panel displays. Support 24 can be formed of any material getterlayer 22 will adhere to well. However, it is advantageous that support24 be able to maintain good mechanical strength and have low outgassingcharacteristics at temperatures as high as an activation temperature ofthe getter material of getter layer 22. The materials that best meetthese requirements include metals and their alloys, in particularaluminum, steel, titanium, and nickel-chromium alloys, and silicon,ceramics and glasses. Support 24 has essentially the same shape as asubstrate used in a deposition process so that the getter device 20 willhave essentially the same shape as a substrate used in a depositionprocess.

Getter layer 22 can be formed of any getter material known in the art,however, some compositions will be preferable for particularapplications due to various considerations, as described above withrespect to getter body 12. Additionally, however, getter layer 22 shouldbe formed of a getter material that can be readily deposited by thechosen deposition technique. As previously described, getter layer 22can be deposited on a support 24 by PVD. Additionally, getter layer 22can be deposited in the form of a powder by spraying a suspension ofparticles of the desired getter material in a suitable solvent onto aheated support 24, or by either an electrophoretic or serygraphictechnique.

As shown in FIG. 2, getter device 20 can further include a rim portion26. The serygraphic technique described above is well suited for theformation of patterned deposits, such as shown in FIG. 2, where aportion of the support 24 is coated with getter layer 22 while rimportion 26 remains uncoated. Rim portion 26 should be no larger thannecessary because any increase in rim portion 26 detracts from theamount of area devoted to getter layer 22 and therefore reduces thegettering capacity of getter device 20. Rim portion 26, however, shouldprovide enough uncoated area around the perimeter of the of support 24so that the getter device 20 can be manipulated by automated handlingequipment without tangs, clamps, or guides coming into contact with thegetter layer 22. The acceptable width for rim portion 26 will varyaccording to the type of substrate the getter device 20 is modeled on,however, in most instances it will be in the range of approximately 2 mmto 10 mm.

FIG. 3 illustrates a getter device 30 formed of a first getter layer 32of a getter material deposited onto a first face 33 of a support 34 anda second getter layer 36 of a getter material deposited onto a secondface 37 of support 34. Support 34 can be formed of any material that thegetter layers 32 and 36 will adhere to well. However, it is advantageousthat the support 34 be able to maintain good mechanical strength andhave low outgassing characteristics at temperatures as high as thehigher activation temperature between the getter materials of getterlayers 32 and 36. The materials that best meet the requirements forsupport 34 include metals and their alloys, in particular aluminum,steel, titanium, and nickel-chromium alloys, and silicon, ceramics andglasses. Support 34 has essentially the same shape as a substrate usedin a deposition process so that the finished getter device 30 will haveessentially the same shape as a substrate used in a deposition process.

Getter layers 32 and 36 can be formed of any getter material known inthe art, however, some compositions will be preferable for particularapplications due to various considerations, as described above withrespect to getter body 12. Additionally, however, getter layers 32 and36 should be formed of getter materials that can be readily deposited bythe chosen deposition technique. As previously described, getter layers32 and 36 can be deposited on a support 24 by PVD. Alternately, getterlayers 32 and 36 can be deposited onto support 34 in the form of apowder by spraying a suspension of particles of the desired gettermaterial in a suitable solvent onto a heated support 34, or by eitherelectrophoretic or serygraphic techniques. It should be noted that insome embodiments getter layer 32 will comprise a different gettermaterial than getter layer 36.

As shown in FIG. 3, getter device 30 can further include a first rimportion 38 on first face 33 and a second rim portion 39 on second face37. Rim portions 38 and 39 should be no larger than necessary becauseany such increase necessarily detracts from the amount of area devotedto getter layers 32 and 36 and therefore reduces the gettering capacityof getter device 30. Rim portions 38 and 39, however, should provideenough uncoated area around the perimeter of the support 34 so thatgetter device 30 can be maintained in a vertical position by tangs, orcan be manipulated by automated handling equipment that commonly hold orclamp substrates by their edges.

The present invention also encompasses a method for reducing evacuationtime and contamination in a vacuum chamber. As shown in FIG. 4, themethod 100 begins with act or operation 102, providing a vacuum chamberhaving a sample holder disposed therein for supporting a substrate,followed by act or operation 104, providing automated handling equipmentconfigured to load and unload a substrate with respect to the sampleholder. Next, in act or operation 106 a getter device is loaded into thechamber with the automated handling equipment such that the getterdevice is left supported by the sample holder. In act or operation 108the chamber is pumped by both an external pump and the getter device toachieve a pressure. In act or operation 110 the getter device isunloaded from the chamber using the automated handling equipment.

In act or operation 102 a vacuum chamber is provided having a sampleholder disposed therein for supporting a substrate. A vacuum chamber canbe a deposition chamber, a conditioning chamber, or any other chamberintended to operate at a pressure below normal atmospheric pressure. Thevacuum chamber includes a sample holder disposed therein for supportinga substrate. The sample holder can be a horizontal support fixed to apedestal, as discussed above with reference to semiconductor processing.In other embodiments the sample holder can support a substrate in avertical orientation through the use of tangs. Other sample holdersknown in the art may also be employed.

In act or operation 104 automated handling equipment is provided. Theautomated handling equipment is configured to load and unload asubstrate with respect to the sample holder. Automated handlingequipment for transferring substrates in and out of vacuum chambers arewell known in the art as discussed above.

In act or operation 106 a getter device is loaded into the vacuumchamber by the automated handling equipment. The getter device is placedin the chamber such that it is supported by the sample holder. Thegetter material of the getter device may either be activated orunactivated in act or operation 106. Since the sorption of impurities bygetter materials is an exothermic process, it is necessary to keep thesum of the partial pressures of all reactive gases below about 10⁻³ mbarwhenever a getter material is in an activated state in order to preventthe getter material from combusting. Consequently, in those embodimentsin which an activated getter is introduced into the vacuum chamber, actor operation 106 further includes reducing the pressure within thechamber below about 10⁻³ mbar before loading the getter device.Pressures of less than about 10⁻³ mbar can be achieved with medium andhigh-vacuum pumps such as turbomolecular or cryogenic pumps after aninitial pump-down with a low-vacuum mechanical pump. It will beappreciated that an unactivated getter can be loaded in act or operation106 into the chamber by hand as well as by automated means. It will befurther appreciated that an activated getter can be loaded when thepressure is above about 10⁻³ mbar so long as the sum of the partialpressures of all of the reactive gases remains below about 10⁻³ mbar.

In act or operation 108 the vacuum chamber is pumped by both an externalpump and the getter device to achieve a desired pressure. The desiredpressure, for example, can be a base pressure. A base pressure for CVDcan be in the range of 10⁻⁸-10⁻⁹ mbar and is the most desirable pressureat which to perform a deposition from the standpoint of film quality.For PVD a base pressure can be on the order of 10⁻⁸ mbar and may beachieved prior to the vacuum chamber being back-filled with an inert gasas described above. Alternately, the desired pressure can be a presetvalue above the level of the base pressure. As a further alternative,the desired pressure may be a pressure at which the level of one of morecontaminants falls below some predetermined value. For example, a massspectrometer connected to the vacuum chamber can measure the levels ofreactive gases within the chamber and when one or more reactive gaseshave been sufficiently removed the desired pressure has been achievedand act or operation 108 is completed.

The external pump is a pump located outside of the vacuum chamber thatis in fluid communication with the interior of the vacuum chamber. Theexternal pump, for example, can be a turbomolecular pump or a cryogenicpump or in some embodiments a plurality of pumps. The external pump canpump non-reactive species as well as reactive species. Here, pumping bythe getter device refers to the sorption of reactive species from theatmosphere within the vacuum chamber by the getter material of thedevice. The getter device and the external pump, working in combination,can evacuate a vacuum chamber to a desired pressure more quickly thaneither one alone. Further, the external pump and the getter deviceworking in combination can achieve a lower base pressure than either onealone. Once a desired pressure has been achieved, in act or operation110 the getter device is unloaded from the chamber by again using theautomated handling equipment.

FIG. 5 illustrates another method 120 of the present invention. Method120 proceeds essentially as method 100 through acts or operations102-106. In act or operation 122, however, the vacuum chamber isevacuated with an external pump to achieve a vacuum of below about 10⁻³mbar. This is accomplished essentially as it is in act or operation 102,as described above with reference to method 100. Next, in act oroperation 124 the getter material of the getter device is activated by aheater configured to heat a substrate supported on said sample holder.In some embodiments the heater is located within the vacuum chamberproximate to the sample holder, while in other embodiments the heater isdisposed within a pedestal that includes the sample holder. In stillother embodiments the heater is located outside of the vacuum chamberand heats a substrate with radiant heat projected through a quartzwindow. Whatever the source of heat, in act or operation 124 the gettermaterial of the getter device is heated to at least its activationtemperature for a sufficient length of time for the activation to becomplete. The particular time and temperature employed will varyaccording to several parameters including the type of heater used, theparticular getter material, and the thickness of the deposit or thethickness of the getter device in those embodiments that do not includea support. Generally, however, the activation temperature will bebetween about 300° C. to about 700° C., and the activation will takebetween about ten minutes and about one hour.

In act or operation 126 the chamber is pumped by both an external pumpand the getter device to achieve a pressure. This is accomplished inessentially the same manner as act or operation 108 in method 100. Inact or operation 128 the getter device is unloaded from the chamberusing the automated handling equipment. This is likewise accomplished inessentially the same manner as act or operation 110 in method 100.

FIG. 6 shows yet another method 130 of the present invention. Method 130proceeds essentially as method 100 through acts or operations 102-108.In act or operation 132, however, at least one preliminary operation isperformed while the getter device remains within the chamber. Forexample, in a PVD deposition chamber one preliminary operation would becleaning a target by performing a burn-in. It will be apparent that thegetter device will serve as a dummy substrate. Even though the getterdevice is coated with the target material and quickly loses its abilityto getter impurities, use of the getter device in place of a dummysubstrate saves time by eliminating the need to first remove the getterdevice and then retrieve a dummy.

FIG. 7 shows still another method 140 of the present invention. Method140 is a process for depositing a thin film and proceeds essentially asmethod 100 through acts or operations 102-110. Thereafter, in act oroperation 142, a substrate is loaded into the vacuum chamber with theautomated handling equipment so that the substrate is supported on thesample holder. Finally, in act or operation 144 a thin film is depositedon the substrate. It will be appreciated that a thin film preparedaccording to method 140 can have fewer defects because the use of thegetter device allows the deposition to be performed in a cleanerenvironment. Thus, use of method 140 improves yields where products arefabricated at least in part through the deposition of a thin film on asubstrate. It will also be appreciated that because method 140 reducesthe time necessary to achieve a desired vacuum level use of method 140can improve yield per unit of time.

It will be appreciated that the getter device of the present inventioncan be used at times other than at the beginning of a production run.Consequently, in some embodiments of the method of the presentinvention, after a thin film is deposited in act or operation 144, thecoated substrate is removed and acts or operations 142 through 144 arecycled through repeatedly in order to deposit thin films on a pluralityof substrates. Because each new substrate can introduce contaminationinto the chamber, in some of these embodiments the cycle can beinterrupted after a set number of substrates have been processed andacts or operations 106 through 110 can be repeated. Alternately, insteadof reintroducing the getter device into the vacuum chamber after a setnumber of substrates have been processed, the getter device can bereintroduced only as needed. In these embodiments the need forreintroducing the getter device can be determined by monitoring thedegree of contamination within the chamber, for example, with a massspectrometer connected to the chamber. Thus, when the contaminationrises above a predetermined value the cycle of depositions isinterrupted and acts or operations 106 through 110 are repeated.Additionally, after the last substrate in a production run has beencoated, acts or operations 106 through 110 can be repeated in order toimprove conditions in the vacuum chamber in preparation for the nextproduction run.

FIG. 8 shows still another method 150 of the present invention. Method150 is a process for reducing contamination in a vacuum chamber similarto method 100 but differing in that the getter material of the getterdevice is activated in a chamber separate from the vacuum chamber. Inact or operation 102 a vacuum chamber is provided having a first sampleholder disposed within for supporting a substrate. In act or operation152 an activation chamber is provided having a second sample holderdisposed within for supporting a substrate and a heater configured toheat the substrate. The activation chamber is preferably apreconditioning chamber that ordinarily is used to heat substrates thatare then moved onto a subsequent processing step such as a thin filmdeposition. A separate chamber to heat substrates is commonly providedto improve the over-all efficiency of a fabrication system. Similarly,greater efficiency can be obtained in the use of the getter devices ofthe present invention by activating the getter material in a chamberseparate from the deposition chamber. As discussed above, the beater canbe disposed within the activation chamber and proximate to the sampleholder or within a pedestal that includes the sample holder.Alternately, the heater can be located outside of the activation chamberand project radiant heat onto the getter device through a quartz window.

In act or operation 154 automated handling equipment is provided. Theautomated handling equipment is configured to load and unload asubstrate with respect to the first and second sample holders. Automatedhandling equipment for transferring substrates in and out of vacuumchambers are well known in the art as discussed above.

In act or operation 156 a getter device is loaded into the activationchamber by the automated handling equipment. The getter device is placedin the activation chamber such that it is supported by the second sampleholder. Since the getter material is not yet activated when placed onthe second sample holder, it is not necessary that the pressure in theactivation chamber be below about 10⁻³ mbar.

In act or operation 158 the getter device is heated to activate thegetter material. To perform act or operation 158 a pressure of less thanabout 10⁻³ mbar must be obtained in the activation chamber to preventcombustion of the getter material. As previously described, pressures ofless than about 10⁻³ mbar can be achieved with medium and high-vacuumpumps such as turbomolecular or cryogenic pumps after an initialpump-down with a low-vacuum mechanical pump. It will be appreciated thata pressure of less than about 10⁻³ mbar may be obtained either beforethe getter device is loaded in act or operation 156, or after the getterdevice is loaded as part of act or operation 158. Once a safe pressurehas been obtained and heating is commenced, the getter material of thegetter device is heated to at least its activation temperature for asufficient time for the activation to be complete. Generally, theactivation temperature will be between about 300° C. to about 700° C.,and the activation will take between about ten minutes and about onehour.

In act or operation 160 the getter device is transferred from theactivation chamber to the vacuum chamber with the automated handlingequipment such that the getter device is supported on the first sampleholder. Thereafter, in act or operation 162 the vacuum chamber is pumpedwith an external pump and the getter device to achieve a pressure, andin act or operation 164 the getter device is unloaded from the chamberwith the automated handling equipment. Act or operation 162 isessentially the same as act or operation 108, and act or operation 164is essentially the same as act or operation 110.

The invention will be further illustrated by means of the followingexamples. Example 1 describes a typical pump-down cycle for a PVDdeposition chamber and Curve 1 in FIG. 9 illustrates a measured pressurein the chamber during that cycle. Example 2 describes a pump-down cyclefor the same PVD deposition chamber as in Example 1 employing a getterdevice of the present invention. Curve 2 in FIG. 9 illustrates themeasured pressure in the chamber during the cycle employing the getterdevice.

EXAMPLE 1

The pressure in a PVD deposition chamber was continuously monitoredwhile a pump-down cycle was performed. The measured pressure in thechamber during this cycle is shown in FIG. 9 as curve 1. The chamberincluded a pedestal supporting a sample-holder and further included aninternal electrical resistance heater. The chamber also included twoquartz lamps located on two opposing side walls. A rotary pump and acryogenic pump were connected to the chamber by a port to perform thepump-down. In order to measure pressures in the chamber below about 10⁻⁵mbar a Bayard-Alpert manometer was employed.

At the beginning of the test the chamber was sealed and pumping wasinitiated. Approximately a half hour into the test, when the pressure inthe chamber reached a value of about 10⁻⁶ mbar, a baking procedure wasperformed by heating the interior of the chamber with the quartz lampsand heating the electrical resistance heater to 500° C. After a two hourbake the chamber was allowed to cool while pumping was continued. FromCurve 1 in FIG. 9 it can be seen that during the bake the pressure inthe chamber increased by about half an order of magnitude. As thechamber was cooled under continuous pumping the pressure fell to aPreset pressure P at approximately 5 and a quarter hours into the testand thereafter reached a base pressure somewhat higher than 10⁻⁸ mbar atapproximately 7 hours into the test.

EXAMPLE 2

The pressure in the PVD deposition chamber used in Example 1 wascontinuously monitored while a pump-down cycle using a getter device ofthe present invention was performed. The measured pressure in thechamber during this cycle is shown in FIG. 9 as curve 2. Initially, anon-activated getter device was placed on the sample holder within thechamber. The getter device consisted of a silicon wafer support having adiameter of about 200 mm and a deposit of getter material on one face.The getter material used was St 121, described above, and was depositedby screen printing to create a layer approximately 150 μm thick. Theevacuation procedure described in Example 1 was then repeated. Duringthe baking procedure, the temperature of the getter device was raised toabout 500° C., primarily by the internal electrical resistance heater.The getter material was thus activated during the baking.

From Curve 2 in FIG. 9 it can be seen that during the bake the pressurein the chamber increased, but only slightly. As the chamber was cooledunder continuous pumping the pressure fell to a Preset pressure P atapproximately 4 and a quarter hours into the test and thereafter reacheda base pressure slightly below 10⁻⁸ mbar at approximately 7 hours intothe test.

As can be easily seen by comparing curves 1 and 2 in FIG. 9, the use ofthe getter device according to the method of the present inventionproduces two clear advantages over the prior art. The first advantage isthat Preset pressure P was achieved in approximately 80% of the timerequired under the prior art, saving about an hour. The second advantageis that a base pressure was achieved by both the present invention andthe prior art in approximately the same length of time, but the basepressure achieved by the present invention was significantly lower.Thus, the present inventions allows for a lower base pressure andconsequently a cleaner environment in which to deposit thin films.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered illustrative and not restrictive, and the invention is not tobe limited to the details given herein, but may be modified within thescope and equivalents of the appended claims.

1. An easily loaded and unloaded getter device for reducingcontamination in a vacuum chamber, comprising: a getter body havingessentially a shape of a substrate used in a deposition process, wherebysaid getter body may be loaded and unloaded with respect to said chamberby automatic handling equipment configured to load and unload saidsubstrate.
 2. The getter device of claim 1 wherein said getter body hasa thickness between about 0.5 mm and about 5 mm and a lateral dimensionbetween about 10 cm and about 100 cm.
 3. The getter device of claim 1wherein said getter body has essentially a circular shape and athickness between about 0.5 mm and about 1 mm and a diameter betweenabout 150 mm and about 300 mm.
 4. The getter device of claim 3 whereinsaid circular shape includes a flat.
 5. The getter device of claim 1wherein said getter body has essentially a rectangular shape, athickness between about 1 mm and about 5 mm and a lateral dimensionbetween about 10 cm and about 100 cm.
 6. The getter device of claim 1wherein said getter body is formed essentially of a powder of at leastone getter material.
 7. The getter device of claim 1 wherein said getterbody comprises a support and a first getter layer formed of at least onedeposit of a getter material on a first face of said support.
 8. Thegetter device of claim 7 wherein said support is formed of a materialchosen from the group including metals, metallic alloys, silicon,ceramics, and glasses.
 9. The getter device of claim 7 wherein saidsupport is formed of aluminum.
 10. The getter device of claim 7 furthercomprising a second getter layer formed of at least one deposit of agetter material on a second face of said support.
 11. The getter deviceof claim 7 further comprising an uncoated rim portion on said first faceof said support.
 12. The getter device of claim 10 further comprising anuncoated rim portion on said first face of said support and an uncoatedsecond rim portion on said second face of said support.
 13. The getterdevice of claim 6 wherein said getter material is chosen from the groupincluding zirconium, titanium, niobium, tantalum, and vanadium metals,alloys thereof, and alloys thereof further including at least one ofchromium, manganese, iron, cobalt, nickel, aluminum, yttrium, lanthanum,and rare earth elements.
 14. The getter device of claim 7 wherein saidgetter material is chosen from the group including zirconium, titanium,niobium, tantalum, and vanadium metals, alloys thereof, and alloysthereof further including at least one of chromium, manganese, iron,cobalt, nickel, aluminum, yttrium, lanthanum, and rare earth elements.15. A method for reducing evacuation time and contamination in a vacuumchamber, comprising: providing a vacuum chamber having a sample holderdisposed therein for supporting a substrate used in a depositionprocess; providing automated handling equipment configured to load andunload said substrate with respect to said sample holder, loading agetter device including a getter material and having essentially a shapeof said substrate into said chamber with said automated handlingequipment such that said getter device is supported on said sampleholder; pumping said chamber with an external pump and said getterdevice to achieve a desired pressure; and unloading said getter devicefrom said chamber with said automated handling equipment.
 16. The methodof claim 15 wherein providing a vacuum chamber further includesevacuating said chamber with an external pump to achieve a vacuum ofbelow about 10⁻³ mbar.
 17. The method of claim 15 further comprisingbefore pumping said chamber with said external pump and said getterdevice: evacuating said vacuum chamber with an external pump to achievea vacuum of below about 10⁻³ mbar; and activating said getter materialwith a heater configured to heat said substrate when supported on saidsample holder.
 18. The method of claim 15 wherein said vacuum chamber,as provided, is at a pressure above about 10⁻³ mbar, and wherein a sumof partial pressures of all reactive gases within said vacuum chamber isbelow about 10⁻³ mbar.
 19. The method of claim 18 further comprisingbefore pumping said chamber with said external pump and said getterdevice: activating said getter material with a heater configured to heatsaid substrate when supported on said sample holder.
 20. The method ofclaim 15 further comprising after achieving said desired pressureperforming at least one preliminary operation within said chamber. 21.The method of claim 20, wherein said at least one preliminary operationincludes cleaning a target.
 22. A method for reducing evacuation timeand contamination in a vacuum chamber, comprising: providing a vacuumchamber having a first sample holder disposed therein for supporting asubstrate used in a deposition process; providing an activation chamberhaving a second sample holder disposed therein for supporting saidsubstrate and a heater configured to heat said substrate supported onsaid second sample holder; providing automated handling equipmentconfigured to transfer said substrate between said first and secondsample holders; loading a getter device including a getter material andhaving essentially a shape of said substrate into said activationchamber with said automated handling equipment such that said getterdevice is supported on said second sample holder; heating said getterdevice with said heater to a temperature and for a time sufficient toactivate said getter material; transferring said getter device from saidactivation chamber to said vacuum chamber with said automated handlingequipment such that said getter device is supported on said first sampleholder; pumping said vacuum chamber with an external pump and saidgetter device to achieve a desired pressure; and unloading said getterdevice from said chamber with said automated handling equipment.
 23. Amethod for depositing a thin film on a substrate, comprising: providinga vacuum chamber having a sample holder disposed therein for supportinga substrate used in a deposition process; providing automated handlingequipment configured to load and unload said substrate with respect tosaid sample holder; loading a getter device including a getter materialand having essentially a shape of said substrate into said chamber withsaid automated handling equipment such that said getter device issupported on said sample holder; pumping said chamber with an externalpump and said getter device to achieve a desired pressure; unloadingsaid getter device from said chamber with said automated handlingequipment; loading a substrate into said chamber with said automatedhandling equipment such that said substrate is supported on said sampleholder; and depositing a thin film on said substrate.
 24. The method ofclaim 23 wherein said vacuum chamber, as provided, is at a pressureabove about 10⁻³ mbar, and wherein a sum of partial pressures of allreactive gases within said vacuum chamber is below about 10⁻³ mbar. 25.The method of claim 23 further comprising before pumping said chamberwith said external pump and said getter device: activating said gettermaterial with a heater configured to heat said substrate when supportedon said sample holder.